Process of and apparatus for isolating argon



March 27, 1928.

G. R. FONDA PROCESS OF AND APPARATUS FOR ISOLAIING ARGON 2 Sheets-Sheet Filed March 19. 1924 Im/entov' Gov-ton Rjrohcla.,

I'HsAttorney.

March 27, 1928. O 1,664,205

G. R. FoNDA PROCESS OPA AND APPARATUS FOR ISOLATING AEGON Filed March 19. 1924 2 Sheets-Sheet 2 lPatented Mar. 27, 1928.

UNITED STATES PATENT oFFlcE..

GOBTON R. FONDA, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELEGIBIO COMPANY, A CORPORATION OF NEW YORK.

Application filed Hai-ch 19, 1924. Serial No; 700,211.

The present invention relates to the separation of argon from air, and it is the object of my invention to improve the thermal efliciency of a process whereby a gaseous concentrate rich in argon may be produced. From this concentrate, pure argon may be isolated by chemical or other convenient means.

Air contains about 21 per cent oxygen,

about 78.1 per cent nitrogen, and about .9

per cent of argon. There are other minor constituents which need not be considered.

In order to isolate argon, the air heretofore has been liquefied as a Whole, and then subjected to rectification to separate the liquid into fractions which respectively consist largely of nitrogen and oxygen, the rectification process being so carried out that the argon is concentrated either in the nitro en or in the oxygen fraction. The fraction containing the argon is subjected to a second rectification to concentrate the argon still further.

In accordance with my present invention, I have provided a separation` process of greater efficiency by initially liquefying only a part of the air, discarding the unliqueied residue, and producing an argon concentrate from the liquefied portion only.

I have found that a noteworthy concentration of argon occurs as a result ofsuch an initial partial li uefaction. If 5 per cent of the air is lique ed, for instance, I find that the liquid contains about 2.4 per cent 85 argon as compared with about 0.9 per cent which it would have if it had been completely liquefied. As this 2.4 per cent however,

represents only about 12 per cent of the original content in air, it is more desirable 40 to liquefy a greater 'proportion of thel air initially, thus maintaining as far as possible the advantage of increased concentration of the argon, but obtaining as well a greater fraction of the available argon.

'When about thirty-five per cent of the air is liquefied initially, a liquid is obtained whose argon content has been raised to 1.5 per cent and which represents about 54 per cent of the available argon in the air. As the fraction of the original air input which is liquefied becomes greater the advantage of partial liquefaction necessarily becomes progressively less, so that ordinarily only about a third of the input of air should be liquefied.

My invention includes a new arrangement of apparatus whereby this process may be efficiently carried out.

The laccompanying drawing illustrates somewhat diagrammatically two forms of appJaratus adapted to carry out processes em odying my invention, and also embodying novel structural features of my invention. Fig. 1 illustrates an apparatus wherein the argon is separated with the nitrogen; and Fig. 2 illustrates an alternative apparatus wherein the argon is separated with the oxygen.

In the apparatus shown in Fig.. 1 the oondensate produced by partial liquefaction of the air is rectified to produce a liquid consisting largely of oxygen and a gaseous portion consisting largely of nitrogen a'nd containixg most of t e argon of the original lique ed portion.

The operation proceeds as follows: A ir at a pressure somewhat above atmosphericpressure and preferably in the range of about two to five atmospheres is supplied by the. pipe 4 to the heat interchanger 5, where it Y is precooled by the cold gases which are being discharged into the atmosphere. The cooled air passes on by means of a conduit 6 to the liquefying pipesd?, which are immersed first in li uid air (formed as later described), the llquid air being replaced when the operation is under way by liquid ,l

oxygen which accumulates in the kettle 8 at the bottom of a column 9, at a temperature of about degrees Kelvin. The liquefying conditions are regulated to produce a' liquid portion which may constitute about one-third of the original air contentl (preferably thirty-live per cent) this liquid fraction being passed through the conduit 10 into a coill 11, which is immersed in the liquid mixture in the kettle 12 (which consists largely of argon) at the bottom of a column 13, where it is further cooled. The liquid then passes through a conduit 14 into an under-cooling chamber 15, which is maintained at a temperature' of about 75 to 77 K. as will behereinafter more fully described. The pressure of the gas-is reduced to a pressure slightly above atmospheric pressure by a valve 2 in the pipe 10. It is introduced at this temi perature by aconduit 16 to the top Iof the column 9 and conveyed in a coll 17 to a nitrogen, with substantially all of the argon in the original liquefied portion of the air, is drawn ottl from the top of thecolumn 9 by means of a conduit 22 containing a valve 23 and is delivered to a coil 24 in the undercooling 'chamber 15. A sufliciently low temperaturey prevails in this cooling chamber to cause the nitrogen-argon mixture to liquefy. The liquid is brought by conduit 25 into the rectifying column 13 at a point part Way down. the column '13, as indicated in the drawing, Where it is rectified. From the top of the rectifying column 13a conduit 26 carries the gaseous distillate through a cooling coil 27, where some ofthe argon which tends to escape with the nitrogen from the top of the condensation column 13 is re- -condensed, and returned to the column 13.

Gaseous nitrogen is carried by a valved conduitV 28 through the heat interchanger 5 into the atmosphere, or it is collected, if desired, in any convenient way.

, The argon concentrate, containinor smalll amounts of oxygen and nitrogen, collects as a liquid in the kettle 12 at the bottom of the rectification column 13. Gas from this argon concentrate is drawn oli through a conv duit 29 containing a valve 130 and is passed through the heat interchanger 5 to'increase the thermal eiiiciency of the apparatus.

The low temperature in the cooling chamber 15 is produced conveniently by a supplementary air liquelier 32 at the top 'of the column 13, utilizing from l/g, to 1/2 of the unliquefied air from the first rectifier dise. charged by the conduit 33. Air :from this conduit is compressed by a compressor (not shown) and the compressed air is introduced through a conduit 34 the expanded air escaping through a conduit.37. By this expansion part of the air is liquefied 1n the usual Way. The liquid collects at the bottom of the chamber 32, Where.it overtlows through the conduit'38 into the chamber 15.

Here it is put under a partial vacuum by a pump exhausting through'a conduit 39 so as to boil the liquid at a temperature below the boiling point of pure nitrogen. Its absolute pressureconveniently can be from 1A to% of an atmosphere, corresponding to a teme pure oxygen is drawn off,

perature range of 73.5 to77 K. By this means a temperature is produced in the chamber 15, suiiiciently low to condense Whatever gases are passed therethrough, as described.

In order to start the apparatus into operation it is cooled dovvn to liquid air temperature by the expansion of high pressure air.. The compressed air enters by a-conduit. 4 and passes on through the chamber 5, the conduit 6, the pipes 7, the conduits 10, 14 and 16, until it is finally discharged into the atmosphere through the conduit 19. Expansion occurs at the valve 2 until a portion of the air is liquefied and collects lin the kettle 8 at the bottom of a column 9. Here the liquid air is converted by rectification to liquid oxygen during operation, as already describe In accordance with a process described and claimed in my prior Patent 1,527,639 of February 24, 1925, the argon is concentrated in a gaseous nitrogen fraction which is rectified to produce a gas Psufiiciently high in argon to permit of further concentration by chemical methods. Therefore, generic claims are not made herein, covering broadly the described process of separating atmospheric argon together with gaseous nitrogen from air.

In accordance with an alternate method of operation, the argon is separated first with the oxygen instead of With thenitrogen, the argon being later separated from the oxygen by rectification. An apparatus whereby such a separation may be carried out is illustrated by Fig. 2. The entering air supplied by the valved conduit 4, after passing through the heat interchanger 5, is conducted by a pipe 40 through the coil 41 in the kettle 42 of the column 43 to secure a further cooling, some incidental liquefaction occurring, and then is-passed by a pipe 44 through the branched pipes 45 in the kettle 46 of the column 47 to obtain the partial condensation desired. Theunlique fied portion of air is discharged as in Fig. l by a conduit 19.

The rectification in the column 47 is carried out until the liquid in the kettle 46 contains about 93 to 96 per cent oxygen, a point at Which all of the argon originally liquefied is present in this liquid at a concentration of about 5 per cent. W'hen the oxygen constanthas risen to this value, the liquid is transferred by a conduit 48 through y/a valve 49 to an intermediate region in the column 43, Where its rectification proceeds in the usual Way and as described above. Vapor at the top of the column 43 passes into theundercooling chamber 15', Where it is partially condensed in the coil 50, and to aidb irki) the replt-iication.

u stantia yv ure li uid ox in kettle 42 anld is diawn 0317ig n collects as a gas llo y:sa

through the conduit 53 which is led through the heat interchanger 5. The gaseous argon concentrate is drawn off through conduit 54 from the top'of the column. Gaseous nitrogen is drawn off from column. 47 through a conduit 55, which also is led through the heat interchanger 5. The passage of the liquefied air in the pipes 45 to the coils 56 and 17 by a conduit 16 is similar to the operation described in connection with Fig. 1.

In the description given above, it is vunderstood that the pressure in the rectifying columns is only slightly above atmos heric, being higher in columns 9 and 47 o Figs. 1 and 2 than in the columns 13 and '43 in order to assist in the transfer of the gaseous or liquid product from one column to the next.

The figures do not show means for compressing the air used in the argon separation nor compressors and the temperature interchangers for the portion of air liquefied in the liqueiier-32, asthese features are implied in all liquid air processes.

In addition to the oxygen and-nitrogen obtained, as described above, additional amounts of these gases can be obtained by rectifying in the usual way, the air liquefied for the under-cooling chamber 15..

What I claim as new and desire to secure by Letters Patent of the United States is 1. The method of deriving argon from air which consists in subjecting air to liquefying conditions, regulating said conditions to cause the liquefied portion of the air so treated to be less than the unlique'ed p0rtion, separating the liquid from the gaseous vair, subjecting said liquid to a rectification process to produce liquid oxygen and a gaseous distillate of nitrogen containing most of the argon, reliquefying said distillate and rectifying the same to produce an argon concentrate.

2. The method of separating argon from` the atmosphere which consists in liquefying about 35 per cent of a given quantity o air, discarding the unliquefied portion, rectifying the liquid portion to. produce a liquid consisting largely of oxygen and a gaseous distillate consisting largely of nitrogen and containing most of the argon content of the original liquid portion, reliquefying said gaseous distillate and rectifying the liquid to obtain an argon concentrate.

3. The method of separating argon from I the atmosphere which consists in liquefyin'g a part only of a given volume of air,.dis carding the remaining portion of air, rectifying the resulting liquid to remove oxygen and to produce a fraction containing nitrogen and a higher percentage of argon than is 'rectifying the cooled liquid to produce a fraction consisting largely of oxygen and a second fraction consisting largely of nitrogen and argon, carrying away the oxygen, cooling the nitrogen-argon fraction, rectifying the same Vto produce a gaseous argon concentrate, recondensing the argon, carrying away the gaseous nitrogen, and finally carrylng away an argon concentrate.

5. An apparatus for concentrating argon from air which consists in means for liquefying a portion of an input of air, a conduit for carrying away the unliquefied air, means for producing from said liquid a gaseous nitrogen-argon fraction, a cooling chamber, means for lowering the temperature in said chamber through the intermediary'of the unliqueiied portion of the original air input, means for liquefying the nitrogen-argon fraction in said cooling chamber, and means for rectifying said liquid nitrogen-argon mixture to produce a concentrate rich in argon. v

6. An apparatus for producing a concentrate rich in argon from air which consists l in means for liquefying a portion only of an input of air, means for carrying away the resultin liquid from the unliqueiied portion, means or separately liquefying the latter portion, means for evaporating the resulting liquid under partial pressure, means for fractionating the first portion by successive fractional distillations, and means for condensing the vapors intermediate said distillations through-the intermediary of the heat absorption of the aforesaid liquid evaporating under partial pressure.

7. An apparatus for separating argon vfrom air which consists in means for in part liquefying a given volume of air, means for carrying away the liquid portion to the exclusion of the gaseous portion, means for lfurther cooling said liquid portion, 4means for rectifying said liquid to separate therefrom a mixture of gaseous nitrogen and argon, means for recondensing said gases, and means for rectifying the condensate into gaseous nitrogen and a liquid argon concentrate. y

In witness whereof, I have hereunto set my hand this 18th da of March, 1922.

` RTON R. FONDA. 

